Diagnostic value of CD34 and calretinin immunostaining in the diagnosis of proliferating tricholemmal tumor and trichoblastoma

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BackgroundProliferating tricholemmal tumor (PTT) is a rare neoplasm of controversial biological behavior for which distinction from other more common tumors is essential. Similarly, trichoblastoma (TB) remains a debatable entity that may represent a variation of basal cell carcinoma (BCC). Our goal is to correlate the staining pattern of calretinin and CD34 in these two follicular tumors vs. their major differential diagnoses, invasive squamous cell carcinoma (ISCC) and BCC.MethodDescriptive study of 68 cases: 6 PTT, 22 TB, 20 ISCC, and 20 BCC in a period of 15 years. The diagnosis was confirmed with H&E. The immunohistochemistry results were analyzed and scored positive (weak +, moderate ++, and strong +++) or negative.ResultsCalretinin was expressed in 4/6 cases of PTT and negative in all TB. Only one malignant case of PTT was positive for CD34 (1/2) and negative in all TB cases. Calretinin and CD34 were negative for all ISCC and BCC. The intensities are shown in tables.ConclusionThe diagnosis of these neoplasms is a morphologic diagnosis. However, in those cases where the morphologic aspect is difficult to interpret, calretinin may assist in the diagnosis of PTT, distinguishing the hair follicle tumors with an outer root sheath differentiation. Likewise, CD34 showed significant affinity for the malignant subset of PTT. Calretinin and CD34 did not add any value to the differentiation between TB and BCC. However, this might suggest that both are the same entity with a different morphological permutation.

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