Diagnosis of mycosis fungoides with different algorithmic approaches.

BACKGROUND: Algorithmic scoring approaches for evaluating early cases of mycosis fungoides (MF) provide a degree of diagnostic standardization. At the UWMC, biopsies from clinically concerning cases for MF are individually reviewed by a panel of pathologists and an average score is assigned to each biopsy reflecting the degree of suspicion for a diagnosis of MF; however, such an approach may not be practical outside of an academic center. METHODS: 78 cases characterized in our institution, with the diagnosis confirmed by clinicopathologic correlation/clinical follow-up were evaluated with two different algorithms, based entirely on histologic evaluation (Guitart algorithm) and partial implementation of the ISCL algorithm evaluating histology, immunohistochemistry and T-cell clonality. RESULTS: A receiver operating characteristic curve comparing the results of the two approaches in early MF cases showed no statistical difference between the areas under the two curves. Increased stages of MF showed variable loss of T-cell antigens by immunohistochemistry and higher rates of detectable clonality. CONCLUSION: We could not document a statistically significant advantage of adding ancillary immunohistochemical and molecular testing to careful histologic evaluation in the workup of suspected cases of early MF. A systemic approach to histologic diagnosis by a single pathologist correlated favorably to the MF panel diagnosis.

An 'eruptive' variant of juvenile xanthogranuloma associated with langerhans cell histiocytosis.

The development of juvenile xanthogranuloma (JXG) as a sequel to langerhans cell histiocytosis (LCH) treated with chemotherapy is rare and the hypothesis is intriguing. This is a case of a 19-year-old woman who presented with progressive development of tan-red papules on the axilla and eyelids over a 1.5-year time span. A biopsy of an axillary lesion showed a prominent dermal infiltrate of foamy histiocytoid cells with occasional Touton-type multinucleate giant cells, consistent with JXG. Three years later, the patient presented with additional similar papules on the axilla and vulva as well as a painful mass in the pelvic bone and diabetes insipidus with an associated pituitary mass. An iliac crest bone biopsy showed an eosinophil-rich infiltrate admixed with histiocytoid cells with reniform nuclei, which expressed S100 and CD1a, consistent with a diagnosis of LCH. Nonetheless, an additional axillary papule was once again consistent with JXG, with negative reaction for S100 and CD1a with no Birbeck granules by electron microscopy. This case is unique by the co-existing presentation of multiple cutaneous JXG lesions and internally confined LCH lesions without an apparently associated chemotherapy, corroborating the concept that JXG and LCH may share a common histogenesis.

Collagen-rich variant of benign epithelioid peripheral nerve sheath tumor of the skin.

Schwannoma and neurofibroma account for the majority of cutaneous benign peripheral nerve sheath tumors and usually pose little diagnostic difficulty in their classic forms. In rare instances, however, benign peripheral nerve sheath tumors may display epithelioid morphology and lack otherwise usual features of schwannoma or neurofibroma, making classification difficult. These unusual changes may prompt consideration of other benign neoplasms or a malignancy. Benign epithelioid peripheral nerve sheath tumor (BEPNST) is a somewhat non-specific term recently proposed to describe these neoplasms of imprecise histogenesis. Also diagnostically challenging, rare BEPNST with unusual arrangements of extracellular collagen have been described and reported as neuroblastoma-like schwannoma and collagenous spherulosis. We report a unique case of cutaneous BEPNST with a peculiar arrangement of abundant extracellular collagen, different than the previously observed patterns. Specifically, the neoplastic cells in this tumor were nearly obscured by the collagen, which formed large nodules and compressed the majority of the few remaining tumor cells to the periphery of the lesion. This excessive collagen production emphasizes the importance of adequate sampling to ensure a correct diagnosis.

Lymphomatoid papulosis with CD1a+ dendritic cell hyperplasia, mimicking Langerhans cell histiocytosis.

Although CD1a+ dendritic cells (DC) in cutaneous T-cell lymphomas (CTCL) have been well documented, the presence of large numbers of DC within lymphoid infiltrates can pose a diagnostic difficulty. We present a case of a 70-year-old man with a 3-year history of recurrent red papules and plaques on the extremities and trunk that was referred to our institution, with the diagnosis of Langerhans cell histiocytosis. Skin biopsies showed a wedge-shaped cellular infiltrate in the superficial and deep dermis consisting of two cell populations. Most prominent were clusters of epithelioid cells with grooved nuclei and abundant eosinophilic cytoplasm, which stained with antibodies to CD1a and S-100. A second, less prominent population of atypical lymphocytes, some with enlarged, hyperchromatic and convoluted nuclei, were intermixed. The latter were positive for CD30, CD3 and CD5 and negative for CD20, CD34, CD68, ALK-1 and TdT. T-cell receptor gene rearrangement studies confirmed a clonal T-cell population, which with the clinical history was consistent with the diagnosis of lymphomatoid papulosis. While previous studies have shown an increased density of dermal DC in CTCL, we believe that this represents the first report of an unusually florid DC proliferation mimicking Langerhans cell histiocytosis and masking a lymphoproliferative disorder.

Giant cell rich histiocytic dermatitis/panniculitis associated with thrombocytosis.

An unusual histiocytic dermatitis associated with a lymphoplasmacytic and histiocytic panniculitis appears to represent a previously undescribed disease process. A 56-year-old woman presented with a 5 year history of a violaceous, maculo-papular rash primarily on her legs. It began approximately 8 months before therapy for thrombocytosis. The rash subsequently progressed to form confluent patches and plaques on her torso and arms. The clinical impression was of disseminated granuloma annulare, but multiple biopsies from different sites did not confirm this. Histologic examination revealed a diffuse proliferation of histiocytic cells in the dermis, without well-formed granulomas or necrobiosis. The cells had large, focally irregular nuclei with prominent nucleoli, and were associated with scattered, often bizarre multinucleate giant cells. Immunohistochemistry demonstrated the histiocytic cells to be positive for S100 and CD68 and negative for CD1a. Perivascular siderophages as well as a lymphoplasmacytic and histiocytic panniculitis accompanied the process. The striking cutaneous changes are of unknown etiology but appear to be previously undescribed.