The CTB method was easily implementable under practice conditions (up to the fixation of the microhemtocrit tube), analogous to surgical biopsy submission for histology. Cell tube blocks can increase diagnostic accuracy when the technique is used in tandem after the cytologic evaluation, and the technique allows storage of fluids. Other advantages of CTB were the simplicity, low cost, and separation of erythrocytes from the nucleated cells, which was helpful in hemodiluted samples.

An 11-month-old prepubertal crossbreed female dog was presented with multiple nodular lesions disseminated over the cervical, back, flank, and abdominal regions. The lesions were ulcerated and cauliflowerlike, or nodular and subcutaneous, measuring up to 13 cm in diameter. Cytologic preparations of one of the lesions revealed a uniform population of round to oval cells, with lightly basophilic cytoplasm that contained multiple distinct vacuoles. Frequent mitotic figures and occasional lymphocytes were also observed. The cytologic diagnosis was cutaneous transmissible venereal tumor (TVT) in a progressing growth phase. This was confirmed by histologic and immunohistochemical findings. Vaginal TVT was diagnosed later in the dog's mother. TVT is a contagious neoplasm of sexually mature dogs that usually is transmitted by coitus and affects the genital mucosa. To our knowledge, this is the first report of naturally occurring multicentric TVT in a prepubertal female dog and also is unique in its exclusively cutaneous (no mucosal) involvement. We speculate that transmission of neoplastic cells occurred during cohabitation and social/mothering behavior between the dogs. Despite the atypical clinical presentation, response to chemotherapy with vincristine was excellent, leading to complete regression of the neoplasm without relapse after 6 months.

Background: Cell blocks and immunohistochemistry (IHC) are increasingly recognized as being complementary tools for cytologic diagnostics, especially for neoplastic diseases. Objectives:The study aimed to evaluate the utility of cell tube block (CTB) IHC for refining the diagnosis of effusions in dogs and cats.Methods: Cavitary effusions (n = 25) from dogs and cats classified by cytology as reactive, neoplastic, borderline (suspicious of neoplasia), and chylous were studied.CTB sections were stained with H&E, and immunostained with PAX-5, CD3, pancytokeratin (CK), vimentin, and Wilms tumor 1 protein (WT1) antibodies, according to the cytologic diagnoses. A histologic case series of confirmed normal, reactive, and neoplastic mesothelium and several different carcinomas were included to test the utility of WT1 as a marker of mesothelial cells. Results:CTBs had a layered appearance with reduced background staining. CD3 and PAX5 immunolabeling allowed immunophenotype assessment in all of the lymphoma cases. In carcinomatous effusions, neoplastic cells were CK-positive, WT1negative, and vimentin-negative (except for two cases). Wilms tumor 1 protein was positive in the nuclei of normal, reactive, and neoplastic mesothelial cells, and ovarian carcinomatous cells. Other carcinomas and lymphomas were negative. Conclusions:CTBs are valuable tools to assist in making a diagnosis of cavitary effusions in dogs and cats, and WT1 is a promising marker to differentiate mesothelial from carcinomatous cells. K E Y W O R D Scell blocks, cytology, effusion, immunohistochemistry, mesothelial cells

The manual cytocentrifuge produced cytospins with similar cell yield as the automated cytocentrifuge. Considering the low cost and portability, this new method should be particularly useful for cytologic diagnosis in small clinics, developing countries, and in field studies.