A series of 722 lung carcinomas, surgically resected and typed some years ago according to the 1967 WHO classification, was independently reviewed by 2 observers in order to test the reproducibility of histopathological typing when using the criteria of the 1981 WHO classification. Typing was fully agreed upon in 87% of cases. Agreement was very high for squamous-cell, small-cell and adeno-carcinomas (kappa = 0.87, 0.89 and 0.85, respectively) while adenosquamous (kappa = 0.56) and large-cell (kappa = 0.71) carcinomas were more controversial categories. A consensus diagnosis was formulated for lesions with discrepant diagnoses. When comparing the final typing to the previous typing based on the 1967 WHO classification, squamous- and large-cell carcinomas were reduced respectively by 22% and 33% and adenocarcinomas increased by 94% of the original number. The 1981 "adenosquamous carcinoma" category included 2.8% of the tumours, while the corresponding 1967 category "combined epidermoid and adenocarcinoma" was empty. These changes must be taken into account when considering epidemiological studies, especially those aiming at evaluation of the secular trends of lung cancer by cell type.

A case of superficially invasive cutaneous squamous cell carcinoma (SCC) of the sole containing numerous mucin-producing vacuolated cells resembling "signet-ring" cells is reported. The 2 cellular components of the tumor, both squamous and mucinous, were atypical with pleomorphic nuclei, and expressed the same immunophenotype, consistent in weak and focal positivity for cytokeratin 5/6 and epithelial membrane antigen (EMA) and weak cytoplasmic and nuclear positivity for p16. Real-time PCR genotyping demonstrated the presence of high-risk human papillomavirus (HPV) type 18. We diagnose our case as "cutaneous SCC with mucinous metaplasia" and discuss the differential diagnoses with other skin tumors exhibiting mucin-containing cells, in particular with adenosquamous carcinoma and mucoepidermoid carcinoma. Although HPV 18 is not uncommon in cervico-vaginal pathology, where is often associated with mucinous adenocarcinoma or adenosquamous carcinoma of the cervix, its detection has been rarely reported in cutaneous SCC. In our case, the association of mucinous metaplasia and oncogenic high-risk HPV 18 in a cutaneous SCC may be of interest to the dermatopathologist. Further observations need to confirm whether the histopathologic finding of mucinous metaplasia in an atypical squamous cell proliferation could be a clue for investigating the presence of oncogenic high-risk HPV infection, with particular regard to HPV 18 subtype.

Summary Differentiation of pagetoid cutaneous neoplasms can be very challenging on hematoxylin and eosin-stained sections. We report a singular case of pigmented pagetoid Bowen’s disease showing transitional features between extramammary Paget’s disease and in situ squamous cell carcinoma.