Potential unreliability of normal tissue as positive control in diagnostic immunohistochemistry of poorly differentiated carcinoma

Anurag Joshi (1) , Murali Varma (2) , Bharat Jasani (3) , Sue Wozniac (4)

1 Histopathology
2 Histopathology
3 Histopathology
4 Histopathology

Inclusion of appropriate positive tissue control(s) is an integral part of quality assurance in routine diagnostic immunohistochemistry of tumours. However the antigen content of normal tissue elements constituting the internal/external positive control often exceeds that associated with tumour tissue. We describe two cases in which the tumour was falsely interpreted as immunonegative supported by adequate positivity displayed by the internal positive control. Both cases, a prostate needle biopsy and a TURP specimen, contained poorly differentiated carcinoma that was negative for prostatic markers. A diagnosis of urothelial carcinoma was considered, but tumour tissue in both cases was immunonegative for the urothelial marker 34ßE12 with the internal positive controls (basal cells of benign prostate glands and benign urothelium respectively) showing diffuse positivity. However, repeat immunostaining with a more sensitive method revealed intense diffuse 34ßE12 positivity in the tumour cells in both cases indicating a diagnosis of urothelial carcinoma that was subsequently confirmed by clinical follow-up. We conclude that while benign prostate would be a suitable internal/external positive control when 34βE12 is used as a prostatic basal cell marker, if the same antibody is used as an urothelial marker, the ideal external control would be high-grade urothelial carcinoma.

Mots clés: Medicine

Anurag Joshi, Murali Varma, Bharat Jasani, Sue Wozniac. Potential unreliability of normal tissue as positive control in diagnostic immunohistochemistry of poorly differentiated carcinoma. Histopathology, 2010, 57 (5), pp.760. ⟨10.1111/j.1365-2559.2010.03692.x⟩. ⟨hal-00593445⟩