Is superficial spreading melanoma still the most common form of malignant melanoma?

BACKGROUND: Most epidemiological studies suggest that superficial spreading melanoma is the most common histological subtype of malignant melanoma, but past data may not reflect current patterns of sun exposure or other risk factors. OBJECTIVE: We sought to determine the prevalence of melanoma subtypes among recent specimens in a South Texas dermatopathology practice. RESULTS: Lentigo maligna was the most common subtype of melanoma among the cases studied. Of 771 cases of melanoma reviewed, lentigo maligna and lentigo maligna melanoma accounted for 429 (56%). There were 220 cases of pagetoid (superficial spreading) melanoma (29%). Nodular melanoma with no apparent radial growth phase accounted for 27 cases (4%), and there were 23 cases of acral lentiginous melanoma (3%). The remaining 72 specimens (9%) included cutaneous metastases, spitzoid melanoma, melanoma in situ arising within a nevus, nevoid melanoma, desmoplastic melanoma, and patterns that could not be classified. LIMITATIONS: Although the dermatopathology practice is located in South Texas, most patients are active duty military, military retirees, and military dependents. The majority currently resides in Texas, but the patients have lived in many locations around the world and traveled extensively. Sun exposure patterns and other risk factors may not reflect those of other populations. We were not able to perform subgroup analysis based on ethnicity or skin type as such data were not typically submitted with the specimens. CONCLUSION: Our results challenge the notion that pagetoid (superficial spreading) melanoma is the most common subtype of malignant melanoma, at least in patients with extensive sun exposure. Changing patterns of sun exposure or environmental factors may contribute to the changing epidemiology of malignant melanoma. The current prevalence of subtypes of melanoma should be studied in other populations.

Contiguous lesions in lentigo maligna.

BACKGROUND: Determining the best biopsy technique for a suspected lentigo maligna can be challenging. Because complete excisional biopsy is rarely practical, the physician is left to choose an appropriate area to biopsy. Sampling error can have devastating consequences, especially if the biopsy demonstrates a pigmented lesion that was considered in the clinical differential diagnosis. The presence of a solar lentigo, pigmented actinic keratosis, or reticulated seborrheic keratosis could mislead the pathologist and clinician to the erroneous conclusion that the incisional specimen is representative of the whole, and that no lentigo maligna is present. OBJECTIVE: We have often observed the presence of a contiguous pigmented lesion adjacent to lentigo maligna. The current study was designed to determine how frequently this phenomenon occurs. METHODS: We studied Mohs debulking specimens of lentigo maligna, and broad shave biopsy specimens of pigmented lesions on heavily sun-damaged areas of the skin proven to be lentigo maligna. RESULTS: Contiguous pigmented lesions were present in 48% of the specimens. The most common lesion was a benign solar lentigo (30%), followed by pigmented actinic keratosis (24%). CONCLUSION: Recognition of this phenomenon may prevent misdiagnosis of lentigo maligna related to sampling error.

Atypical junctional melanocytic proliferations in benign lichenoid keratosis.

Melanocytic lesions with lichenoid regression may mimic a benign lichenoid keratosis (BLK) histologically. A total of 336 BLKs were reviewed and deeper sections obtained to determine the frequency of this phenomenon. Two cases (0.6%) showed at least 1 melanocytic nest or junctional multinucleated melanocyte (starburst melanocyte) on deeper sections confirmed by MART-1 immunostaining. Both of these cases demonstrated solar elastosis, and 1 case had an effaced rete ridge pattern. Not included in the histological study are 5 additional cases in which the initial slide showed only lichenoid dermatitis, but deeper sections obtained before to the initial sign-out revealed a melanocytic proliferation. These 5 cases would have been signed out as "consistent with BLK" if deeper sections had not been obtained. Fluorescent in situ hybridization (FISH) was performed on 3 cases; in each case, the melanocytes demonstrated a loss of chromosome 9p21 DNA copy number. The finding of nests of genetically altered melanocytes on severely sun-damaged skin strongly suggests that these cases represent lichenoid regression of melanoma in situ. Pathologists should approach a diagnosis of BLK cautiously in the setting of severely sun-damaged skin.

A case of bullous pemphigoid limited to psoriatic plaques.

Psoriasis occurs with increased incidence in patients with bullous pemphigoid (BP). In this article, we describe the seventh reported English literature case in which the bullous lesions were limited to psoriatic plaques, and we discuss the pathophysiologic mechanisms that might explain this phenomenon. Treatment with acitretin quickly cleared both psoriatic and bullous lesions, suggesting a direct link between the psoriatic inflammatory process and the evolution of bullous lesions.

Infantile digital fibroma treated with mohs micrographic surgery.

BACKGROUND: Infantile digital fibroma (IDF) is a rare benign fibrous tumor of childhood that frequently recurs despite local excision. Conservative, nonsurgical management may result in regression and/or joint deformity. OBJECTIVE: To describe the histologic features of IDF and discuss a case excised using Mohs micrographic surgery (MMS). METHODS: Case report and review of the clinical, histologic, and ultrastructural features. RESULTS: Characteristic inclusion bodies of actin were identified with hematoxylin and eosin, Masson's trichrome, and rapid actin immunostain. The tumor was debulked and the majority was removed after one stage of MMS, except where the deep margin approached the joint space. The defect healed by secondary intention. At 2 years the patient had no recurrence or functional joint deformity. CONCLUSION: MMS is a surgical treatment option for IDF.

Gloves and socks syndrome: early and late histopathologic features.

BACKGROUND: Gloves and socks syndrome (GSS) is a recently described exanthem, most commonly caused by parvovirus B19. OBJECTIVE: Our purpose was to describe both early and late histopathologic features of GSS. METHODS: We performed histopathologic examination of biopsy specimens from a case of GSS and reviewed all the English-language literature reports of GSS to compare the reported histologic descriptions. RESULTS: A total of 46 cases of GSS have been reported in the English-language literature. In 18 of those, the pathologic features were described. The histologic features of the current case evolved from a nonspecific superficial perivascular lymphocytic infiltrate to a vacuolar interface dermatitis with necrotic keratinocytes, erythrocyte extravasation, and a superficial perivascular and interstitial lymphocytic infiltrate. CONCLUSION: Early lesions of GSS show nonspecific features common to viral exanthems. The late features, of a fully evolved exanthem, demonstrate a vacuolar interface dermatitis with necrotic keratinocytes, a superficial perivascular and interstitial infiltrate, and dermal hemorrhage. These late pathologic features, together with the clinical appearance of GSS, may help distinguish it from other entities.

Trichosporon beigelii infection presenting as white piedra and onychomycosis in the same patient.

Trichosporon beigelii is a fungal organism that causes white piedra and has occasionally been implicated as a nail pathogen. We describe a patient with both hair and nail changes associated with T. beigelii.

Mohs micrographic surgery for melanoma: a case series, a comparative study of immunostains, an informative case report, and a unique mapping technique.

BACKGROUND: Mohs micrographic surgery (MMS) has been established as an alternative to standard surgical excision for local cutaneous malignant melanoma (MM) and melanoma in situ (MIS). The use of melanocyte-specific immunohistochemical stains may improve the diagnostic accuracy of MMS frozen sections. OBJECTIVE: We used MMS with immunostains to determine the maximum and minimum margins required to clear 52 melanomas, mostly MIS of the head and neck. We sought to identify the most sensitive melanocyte immunostain for use in MMS frozen sections and to improve the clinicopathologic correlation of perilesional pigmented lesions. METHODS: We studied 52 consecutive cases of invasive melanoma (n = 10) and MIS (n = 42), tabulating the maximum and minimum margins required for complete tumor resection in any one direction during MMS. In 10 of these cases we studied the relative sensitivity of the immunostains MART-1, S-100, and HMB-45 in Mohs frozen sections. We describe a case highlighting the importance of the increased sensitivity of MART-1. In 12 patients we used a unique mapping technique to help determine the clinical relevance of a total of 35 perilesional pigmented foci. RESULTS: The maximum margin averaged 10.1 mm (range 3-26 mm) for MM and 9.4 mm (range 3-18 mm) for MIS. The minimum margin averaged 7.0 mm (range 3-13 mm) for MM and 5.5 mm (range 3-11 mm) for MIS. For individual tumors, the difference between the minimum and maximum margin averaged 3.7 mm (range 0-13 mm). This difference was >or=5 mm in 38% (20/52) and >or=10 mm in 10% (5/52), highlighting that subclinical tumor extension is often broad and asymmetric. While five of six MM less than 1.0 mm in depth would have been cleared with a routine 1 cm excision, a standard 5 mm margin would have cleared less than one-quarter of the cases of MIS (10/42). In Mohs frozen sections, MART-1 proved superior in sensitivity to both HMB-45 and S-100. Our mapping technique provided clinically relevant histologic correlation for perilesional pigmented lesions, improving the Mohs surgeon's ability to evaluate equivocal foci in frozen sections. CONCLUSION: MM, especially MIS on the head and neck, often exhibits an asymmetric growth pattern, making it quite suitable for treatment with MMS. The use of MART-1 immunostain may improve the diagnostic accuracy of Mohs surgeons. We believe that HMB-45 should not be used to rule out the diagnosis of MIS in equivocal sections because of its inferior sensitivity. We introduce a new mapping technique as an adjunctive measure to aid in the clinicopathologic evaluation of perilesional skin.

Lichenoid tissue reaction in malignant melanoma: a potential diagnostic pitfall.

Lichenoid tissue reactions can occur in malignant melanoma and may cause partial regression of the lesion. We studied a series of melanomas to determine how frequently lichenoid tissue reaction obscures the diagnosis of malignant melanoma. We retrospectively reviewed 342 cases of invasive malignant melanoma and melanoma in situ from the head, neck, chest, and back. Of the 342 cases, 23 (6.7%) had a lichenoid tissue reaction obscuring a portion of the lesion. In 6 cases (1.8%), the lichenoid tissue reaction replaced a major portion of the lesion. Knowledge of this phenomenon can prevent misdiagnosis.