**5. Histopathology**

92 Endometriosis - Basic Concepts and Current Research Trends

Fig. 5. The skin is sutured.

Fig. 6. The excised endometrioma of size 15 cm.

All the excised specimen must be examined histopathologically because of mentioned above reasons (12, 38, 43). The frozen section is advisable (59). Histopatological examination reveals usually ectopic endometrial glands with surrounding cellular stroma, occasionally associated with extravasation of erythrocytes and some inflammatory infiltrates around the glands (5, 33, 38).

Recently, the largest and exhausting study on histopatology of cutaneous endometriosis basing on 73 patients presented Kazakov et al. (31). The excised nodules looked out macroscopically as a gray-white scar-like tissue with or without an evidence of hemorrhage containing tiny cysts when viewed under a magnifying glass. Two cases were excluded from study because of fibrotic granulation tissue in the first and cutaneous endosalpingiosis in the second one with a complete lack of endometriotic tissue in both. The resting cases showed typical endometriotic glands with a characteristic stroma. The müllerian epithelium is apt to show a broad spectrum of metaplastic changes. The authors discovered in glandular component in most of cases tubal metaplasia (61%), less often reactive atypia (23%), oxyphilic metaplasia (15%), hobnail metaplasia (10%), atypical mitoses in glands (6%), mucinous metaplasia (4%), papillary syncytial metaplasia in two cases and hyperplasia in one. The stromal component revealed mostly myxoid changes (69%), less often smooth muscle metaplasia (31%) and in single cases decidual changes, stromal endometriosis, micronodular stromal endometriosis and elastosis. In ¾ of specimens were observed large granular CD56 positive lymphocytes. Quite frequently occurred lipoblast like cells (15%), intranuclear inclusions in adipocytes (10%), atypically appearing myocytes (10%) and spiral arteries (4%). Perineural invasion was present in one case. The authors also advertised, that endometrioid or clear cell cancer can occur in the skin lesions.

Zhang et al. (58) evidenced that bothersome pain caused usually by endometriotic lesion is caused by sensory nerve fibres which are present mainly in deeply infiltrating endometriosis.
