Inflammatory lobular hemangioma (T-cell-rich angiomatoid polypoid pseudolymphoma)-Assessment of FOS/FOSB and lymphoid markers and comparison with epithelioid hemangioma.

BACKGROUND: T-cell-rich angiomatoid polypoid pseudolymphoma (TRAPP) and inflammatory lobular hemangioma (ILH) encompass a spectrum of cutaneous vascular lesions in which a prominent lymphoplasmacytic component may impart a pattern highly reminiscent of low-grade cutaneous lymphoma (pseudolymphoma). Epithelioid hemangioma, including its most common variant angiolymphoid hyperplasia with eosinophilia (ALHE), is a distinct entity associated with FOS and/or FOSB expression detected by immunohistochemistry (IHC). These entities can show significant morphological overlap. METHODS: We performed IHC for FOSB, FOS, and lymphoid markers in a series of TRAPP/ILH and ALHE. RESULTS: We identified 13 cases of ILH/TRAPP, which showed a predominance in CD8+ T-cells (CD8>CD4: 11/13) while FOSB and FOS were expressed in 36% (4/11) and 27% (3/11) of cases, respectively. ALHE (n = 9) showed a predominance in CD4+ T-cell (67%) with FOSB and FOS co-expression in 78% (seven of nine) of the cases. CONCLUSION: We showed, based on FOS and/or FOSB immunohistochemical expression, that there is a possible link between ILH/TRAPP and epithelioid hemangioma/ALHE. The use of FOS and FOSB IHC in the routine diagnostic setting of cutaneous vascular lesions will help to redefine cases of ILH/TRAPP as a subset of these may represent inflammatory variants of epithelioid hemangioma.

Squamoid eccrine ductal carcinoma of the scalp.

An 85-year-old man presented with an ulcerated pruritic nodule on the scalp. Histology of a deep curette specimen showed the typical features of a squamoid eccrine ductal carcinoma: superficial squamous differentiation and deep ductal structures.

Skin cancer: What happens in the laboratory?

BACKGROUND: Skin cancer specimen handling in Australian histopathology laboratories, while largely standardised, exhibits significant variations that affect clinical decision-making and patient outcomes. OBJECTIVE: This article provides clinicians with an understanding of histopathological processes to enhance diagnostic precision, inform surgical margin evaluations and refine management approaches. DISCUSSION: Understanding specimen handling and protocols is vital for accurate interpretation of pathology reports and management of skin cancers. Variations in sampling, examination and sectioning can affect pathological diagnosis and margin assessment. Clinician insights into laboratory processes are crucial for best practice. Retention of specimens and reports allows for further evaluation if clinical circumstances evolve or additional investigations are required.

Immunohistochemistry for FOSB and FOS is a Useful Ancillary Tool in the Diagnosis of Epithelioid Hemangioma but There are Pitfalls in Interpretation Including Expression in Other Vascular Lesions.

Introduction. Epithelioid hemangioma is a benign vascular neoplasm associated with FOS and/or FOSB protein overexpression detected by immunohistochemistry (IHC). Methods. The aim of our study was to determine the co-expression or independent IHC expression of FOS and FOSB in a cohort of epithelioid hemangiomas. We also included two cohorts of other vascular lesions: papillary endothelial hyperplasia and lobular capillary hemangioma / pyogenic granuloma. Results. We identified 50 cases of epithelioid hemangioma, 84% of which were cutaneous and the remaining involved other anatomic locations. Over two thirds of all cases expressed FOSB (68%; 34/50) while FOS immunoreactivity was identified in 46% of all cases. Co-expression of FOSB and FOS occurred in 37% of cases while 76% of all cases stained for at least one of the antibodies. Fifty-eight percent (n = 14/24) and 33% (8/24) of all cases of papillary endothelial hyperplasia expressed FOS and FOSB, respectively. Thirty-two per cent of lobular capillary hemangiomas (n = 8/25) were positive for either FOS or FOSB. Conclusion. In summary, we present the largest cohort of epithelioid hemangiomas assessed with both FOS and FOSB and demonstrated that the use of both antibodies increases the detection rate of these proliferations by 10%. Nonetheless, the use of thresholds may not be appropriate, as only a subset of lesional endothelial cells label with FOS/FOSB. Over half of all cases of papillary endothelial hyperplasia and a third of lobular capillary hemangiomas also displayed immunoreactivity with FOS and/or FOSB.

Analyzing the morphological spectrum of epithelioid fibrous histiocytoma and the immunohistochemical performance of the ALK D5F3 and ALK1 clones.

Epithelioid fibrous histiocytoma (EFH) is a cutaneous neoplasm driven by translocations of the anaplastic lymphoma kinase (ALK) gene, which can be demonstrated by immunohistochemical (IHC) analysis. We analyzed the performance of two ALK clones, D5F3 and ALK1, in a cohort of EFHs and described the range of architectural variation of these lesions. TFE3 IHC was performed in ALK-negative EFHs. We identified 21 cases of EFH, 76.2% of which showed an exophytic appearance and 19% displayed flat architecture. A well-developed epidermal collarette was present in 48% of all cases with just more than a third of all the exophytic lesions presenting as dermal-based nodules. ALK D5F3 expression was identified in 76.2% (16/21) of all cases, but only 68.8% were concordantly positive with the ALK1 clone, indicative of a false-negative stain with ALK1 in 31.2% of the cases. For the subset of cases showing positivity for the ALK1 clone, a marked decrease in the percentage of immunolabelled cells was identified when compared with D5F3 (5-50% vs. 100%, respectively). Five cases (23.8%) did not demonstrate ALK expression for either clone, with 3 of those cases showing nuclear positivity for TFE3 IHC and the remaining 2 cases being double negative (ALK-/TFE3-). In summary, we identified that the prototypically described exophytic appearance with epidermal collarette is present in only less than half of the cases. We also demonstrated that the ALK1 antibody is suboptimal in EFH and should not be utilized in this setting. A subset of ALK-negative cases express TFE3, but double-negative cases occur.