Skin tumors are tumors arising from keratinocyte and from adnexal structures. Immunohistochemistry is very helpful in diagnosis of difficult cases in epithelial skin neoplasms, especially basal cell carcinoma (BCC) which is positive for BerEP4, a keratin marker, and mostly negative for epithelial membrane antigen (EMA). Squamous cell carcinoma cells are positive for EMA and cytokeratin, which are of higher molecular weight than those found in BCC. In contrast to BCC, trichoblastoma and trichoepithelioma are negative for androgen receptors. Of the malignant dermal spindle cell lesions, spindle cell squamous carcinoma is positive to 34 betaE12, desmoplasmic melanoma is positive to S100, and leiomyosarcoma is positive to desmin. Of the malignant pagetoid cells, Paget's disease is positive to CK7 and cam5.2, whereas the pagetoid variant of Bowen's disease is positive to CK 5/6. Melanoma in-situ is positive to both S100 and melan-A. Immunohistochemistry is an extremely valuable adjunct to standard morphologic diagnosis in diagnostic pathology. Diagnosis of epithelial tumor depends largely on morphological features but, in rare cases, immunohistochemical stains are needed for definitive diagnosis.

The Leser-Trélat sign is a rare sign of some malignant tumors and is characterized by the sudden appearance of seborrheic keratosis in association with an underlying malignancy. We describe a 60-year-old Saudi man with mycosis fungoides (MF) who developed numerous, rapidly growing, seborrheic keratoses on his face and back. To the best of our knowledge, this is the first reported case of MF with the Leser-Trélat sign from Saudi Arabia.

Leptodemus minutus, an hemipteran insect previously not known to attack man, was suspected as causing an outbreak of pruritic eruptions in 100 patients in Kuwait.

BackgroundRituximab is useful in patients with rheumatoid arthritis (RA) with persistently active disease despite adequate trials with other disease-modifying antirheumatic drugs (DMARDs).ObjectivesTo determine whether the inhibition of the B cell CD20 receptor by rituximab results in acute hepatitis in BALB/c mice.MethodsTwenty BALB/c mice were studied. Ten mice received subcutaneous (SC) injection of rituximab (0.31mg per 25g body weight per 0.03 ml normal saline) at 0, 1, 2 and 4 weeks. For the control group, 10 mice received a SC injection of normal saline (NS) (0.03 ml). At the 10th week post injection, the mice were sacrificed, and histopathological studies were conductedResultsOf the rituximab-treated group, 1/10 mice died. Liver histology for the rituximab -treated group showed that 7/9 displayed histopathological changes in the lobular cellular infiltrates of eosinophils, lymphocytes and histocytes, in addition to granuloma formation. In contrast, only minimal inflammation was observed in 3/10 mice in the control group (p=0.051).ConclusionTo our knowledge this is the first experimental controlled study demonstrating rituximab may play a role in inducing granulomatous hepatitis with a sarcoidosis-like reaction.References[1] Soliman MM, Hyrich KL, Lunt M, Watson KD, Symmons DP, Ashcroft DM. Rituximab or a second anti-tumor necrosis factor therapy for rheumatoid arthritis patients who have failed their first anti-tumor necrosis factor therapy? Comparative analysis from the British Society for Rheumatology Biologics Register. Arthritis Care Res (Hoboken)2012;64:1108-15.[2] Reuben A. Hepatotoxicity of immunosuppressive drugs. In:Kaplowitz N, DeLeve LD, eds.Drug-induced liver disease. 3rd ed.Amsterdam: Elsevier;2011:569-91.[3] Nard FD, Todoerti M, Grosso V, Monti S, Breda S, Rossi S, et al. Risk of hepatitis B virus reactivation in rheumatoid arthritis patients undergoing biologic treatment: Extending perspective from old to newer drugs. World J Hepatol2015;7:344-361.[4] Greenwald M, Tesser J, Sewell KL. Biosimilars Have Arrived: Rituximab. Arthritis2018;2018.Disclosure of InterestsNone declared

Cutaneous Kaposi sarcoma (KS) is a vascular neoplasm with a broad spectrumclinicopathology. An epithelioid morphology, a rare recent variant of KS, with many variants of KS that may mimic other vascular neoplasms poses a diagnostic challenge. We report on a 75-year-old Saudi man HIV- negative who had been diagnosed with classical KS on the right foot 8 years before the present episode. Histopathological findings of the new lesion included areas showing epithelioid cells with moderate pleomorphism, growing in solid sheets. The epithelioid cells show nuclear enlargement and hyperchromasia mimicking angiosarcoma. Immunohistochemistry shows a strong diffuse nuclear staining pattern for HHV-8 latent nuclear antigen-1 (LNA-1) in the epithelioid as well as the classical spindle cells. A diagnosis of epithelioid Kaposi sarcoma is made, which should be included within the known histological variants of KS. Prior to this case, the epithelioid variant of Kaposi sarcoma has been reported only three times in the literature. Since this variant shares similar clinical and histological features with angiosarcoma, integration of clinical findings and context, histopathologic features and immunohistochemical results is critical in obtaining the correct diagnosis and treatment.