Nonspecificity of Immunohistochemistry for Mycobacteria Species Using a Rabbit Polyclonal Antibody.

CONTEXT.­: Recent publications have featured immunohistochemistry (IHC) as a sensitive tool for detecting Mycobacterium tuberculosis and nontuberculous mycobacteria, but performance is limited to cases suspected to have mycobacterial infection. OBJECTIVE.­: To examine cross-reactivity of a polyclonal antimycobacterial antibody with various types of pathogens, tissues, and inflammatory patterns. DESIGN.­: Surgical pathology files during a period of 6 years were searched, and 40 cases representing a variety of pathogens, tissue types, and inflammatory responses were retrieved. Cases were stained with a rabbit polyclonal antimycobacterial antibody (Biocare Medical, Pacheco, California). The cases and associated histochemical stains, culture, and molecular results were reviewed by 3 pathologists. RESULTS.­: All 8 cases of mycobacterial infection previously diagnosed by other methods were positive for mycobacteria by IHC. In addition, multiple bacterial and fungal organisms and 1 case of Leishmania amastigotes were also immunoreactive with the mycobacterial IHC. CONCLUSIONS.­: Although highly sensitive for mycobacteria, the polyclonal antibody shows significant cross-reactivity with other organisms. This is a sensitive but nonspecific stain that can be used as an alternative confirmation method for mycobacteria, but attention should be paid to inflammatory reaction and organism morphology when IHC is positive to avoid misdiagnosis.

Gastrointestinal, hepatic, and pancreatobiliary involvement by plasma cell neoplasms: clinicopathologic correlations in a retrospective cohort of 116 cases.

AIMS: Plasma cell neoplasms (PCNs) may involve the gastrointestinal (GI) tract in two forms: plasmacytoma (PC), an isolated lesion that lacks marrow involvement, and extramedullary myeloma (EMM). However, previous literature on PCNs involving the GI tract, liver, and pancreas is limited. We evaluated the clinicopathologic features of the largest series of GI PCNs to date. METHODS AND RESULTS: Six institutional archives were searched for GI, liver, and pancreas cases involved with PCNs. Medical records were reviewed for clinical and imaging features. Histopathologic features evaluated included involved organ, tumor grade, and marrow involvement. Overall, 116 cases from 102 patients were identified. The tumors most presented as incidental findings (29%). The liver was most involved (47%), and masses/polyps (29%) or ulcers (21%) were the most common findings. Most cases had high-grade morphology (55%). The majority (74%) of GI PCNs were classified as EMM due to the presence of marrow involvement at some point during the disease course, occurring within a year of marrow diagnosis in 46% of patients. PC was classified in 26% of patients due to the lack of marrow involvement. Most (70%) patients died from disease within 10 years (median 14.1) of diagnosis and more than half (58%) died within 6 months. CONCLUSION: PC and EMM involving the GI tract, liver, and pancreas have a wide range of clinicopathologic presentations. Tumors may occur virtually anywhere in the GI tract or abdomen and may precede the diagnosis of marrow involvement. Both GI PC and EMM are associated with a poor prognosis.

Reproductive Organ Pathology of Individuals Undergoing Gender-Affirming Surgery.

As gender-affirming surgeries become more routine, it is increasingly important for pathologists to recognize the expected histologic changes seen in various tissues secondary to gender-affirming hormone therapy. For example, exogenous testosterone-related squamous atrophy or transitional cell metaplasia of the cervix may be confused for high-grade squamous intraepithelial lesion. In addition to distinguishing between benign and dysplastic/malignant features, pathologists should be mindful of the phrasing of their reports and aim to use objective, nongendered language.

Primary cutaneous follicle center lymphoma with extensive plasmacytic differentiation and t(14;18) in both the lymphoid and plasma cell components.

Primary cutaneous follicle center lymphoma (PCFCL) is the most common cutaneous B-cell lymphoma. The typical immunophenotype includes expression of both CD20 and BCL6, with the majority of cases lacking expression of CD10, BCL2, and the characteristic t(14;18)/IGH-BCL2 rearrangement seen in systemic follicular lymphoma (FL). Plasmacytic differentiation (PD) is an uncommon finding in both systemic and cutaneous FLs and presents a diagnostic challenge when present, leading to the potential for misdiagnosis as marginal zone lymphoma (MZL). Limited reports have described light chain restriction in the plasma cell component of FLs with PD, and rare cases of PCFCL with PD have been described. While the IGH-BCL2 translocation has been identified in a subset of FLs with PD, the presence of the BCL2 translocation in monotypic plasma cells of PCFCL has not been previously described to our knowledge. Here, we report a case of PCFCL with extensive PD in a 77-year-old woman that was favored to represent primary cutaneous MZL on an initial punch biopsy. Excisional biopsy, however, revealed that the atypical lymphocytes expressed CD10, BCL6, and BCL2, while the plasma cell component demonstrated light-chain lambda restriction. FISH studies showed the presence of an IGH-BCL2 translocation in both the lymphocytic and plasmacytic components.