Wide local excision (WLE) using appropriate surgical margins is the standard surgical management for malignant melanoma in situ (MMIS) and primary cutaneous malignant melanoma (MM). The actual width of the histologic margins is frequently not assessed, whereas narrow histologic margins are associated with an increase in local melanoma recurrence. Our objective was to analyze the actual measured histological margins of WLE specimens of MMIS and MM cases and compare them with their recommended surgical margins. A retrospective study of formalin fixed specimens of MMIS and invasive MM treated with WLE from a large university-affiliated dermatopathology laboratory was conducted. Among a total of 164 MMIS and 128 MM cases, 14 MMIS (8.5%) and 7 MM (5.9%) had positive lateral margins. The median histologic margin for MMIS, after a 15% tissue shrinkage adjusted, was 2.7 mm [1.3-3.9] for LM type and 3.9 mm [2.3-5.6] for non-LM type, in contrast to the recommended 5-mm margin. In 96 MM of T1 type (#1.0 mm), the median adjusted histologic margin was 6.7 mm [3.5-9.1] in contrast to the recommended 10-mm margin. These results show that measured and adjusted median histologic margins in WLE specimens in both MMIS and MM of T1 type were significantly narrower than the recommended surgical margins, regardless of anatomic location. These differences are concerning, whether they reflect clinicians' intentional or unintentional deviation from recommended guidelines.

Intraepidermal Merkel cell hyperplasia and Merkel cell carcinoma represent 2 histologically similar-appearing diagnoses with significant differences regarding prognosis and management. We present 1 case of each diagnosis to highlight characteristic histopathologic and immunohistochemical features. Our case of Merkel cell hyperplasia was identified by its small intraepidermal nest of monomorphic cells without atypia or mitoses, which demonstrated cytoplasmic, rather than perinuclear dot, patterning on CK20 staining. This can be contrasted with our case of intraepidermal Merkel cell carcinoma, which, despite a lack of dermal extension, demonstrated large nests of pleomorphic cells with frequent mitoses and apoptoses. The diagnosis was further confirmed by immunohistochemistry because CK20 staining showed classic perinuclear dot patterning. By presenting both diagnoses in parallel, this comparison aims to underscore crucial histopathologic and immunohistochemical similarities and differences.

BackgroundEccrine duct dilatation (EDD) has been noted to occur significantly more often in primary lymphocytic scarring alopecias compared with non‐scarring alopecias, thus serving as a possible histopathologic marker for primary scarring alopecias with a lymphocytic infiltrate. This study aims to determine the presence and role of EDD in primary neutrophilic scarring alopecias.MethodsWe performed a retrospective review comparing primary scarring alopecia (neutrophilic, n = 90; lymphocytic, n = 100) and non‐scarring alopecia (n = 123) for presence of EDD, seen in Boston University School of Medicine between 2013 and 2017.ResultsEDD was more commonly seen in primary neutrophilic scarring (62.2%, 56/90) and primary lymphocytic scarring alopecias (54.0%, 54/100) than in non‐scarring alopecias (25.2%, 31/123) (P < 0.001). Albeit uncommon, non‐scarring alopecias exhibited the biggest ratio of dilated eccrine duct lumen to background duct lumen (14.33), followed by lymphocytic (10.99) and neutrophilic scarring alopecias (6.66).ConclusionEDD is seen more frequently in primary scarring alopecias compared with non‐scarring alopecias and usually found in sections containing inflammation and dermal fibrosis, serving as a possible histopathologic clue for a scarring process. Non‐scarring alopecias have significantly fewer but considerably larger EDD which, may imply a different pathologic cause.

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