Rešitev skrivnostnega kliničnega primera
(01.02.2019) Dober teden dni časa smo vam pustili za razmišljanje in postavitev diagnoze skrivnostnega kliničnega primera meseca – mediastinalna masa pri psu, ki vam ga je predstavilo podjetje Laboklin. Sedaj vam sporočamo pravilno rešitev.
Interpretacija rezultatov
Najverjetnejši vzrok sprememb na krvni sliki in hiperkalcemije je bila neoplazija.
Citološka slika (FNA) mediastinalne mase (Wright-Giemsa, 500x povečava)
Pri citološkem pregledu mediastinalne mase so bili vidni številni majhni in nekaj srednje velikih limfocitov ter nekaj mastocitov. Ob tem so v vzorcu srednje velike epitelne celice, ki se pojavljajo deloma posamično, deloma v majhnih skupkih.
Celice so ovalne ali poligonalne, s svetlo modro citoplazno ter srednje velikim, okroglim do ovalnim, centralno ležečim jedrom.
Jedrni kromatin je fino retikuliran z večinoma enojnim, srednje vilikim, okrolim jedrcem. V ozadju so vidni posamezni eritrociti.
Citološka preiskava kaže na neoplazijo, najverjetneje na thimom, prav tako pa ni mogoče popolnoma izključiti limfoma timusa.
Rezultati PARR preiskave so bili poliklonalni za obe limfocitni populaciji, zaradi česar je bil izključen limfom in se ni opravila biopsija.
Rezultati PTHrP in PTH potrjujejo paraneoplastično etiologijo hiperkalcemije.
DIAGNOZA: THIMOM
TREATMENT AND FOLLOW-UP
The dog underwent median sternotomy to remove the thymoma. Histologic examination of the excised mass confirmed a thymoma (stage III type B2). Two months later the dog was doing well with no respiratory signs and good exercise tolerance.
Histopathology of thymoma from the dog showing aggregates of lymphocytes admixed with clusters of neoplastic cells arranged in sheets (haematoxylin and eosin stain, 10x objective)
SUMMARY
Thymoma is a tumour originating in the thymus. Its development is a consequence of a neoplastic transformation of supporting thymic epithelial cells. Neoplastic cells are frequently accompanied by a non-neoplastic proliferation of lymphoid cells.
Thymoma is the second most common (after lymphoma) cranial mediastinal tumour in the dog but its general prevalence is low. They usually occur in older dogs with the incidence being the highest at the age of 9.
Definitive cytological diagnosis of thymoma can be hampered by a low number of epithelial cells in the sample and both lymphomas and thymomas may be composed of small lymphocytes. This emphasizes the necessity of adjunct diagnostic tests (e.g. clonality testing, flow cytometry) and histopathology.
Paraneoplastic syndromes (e.g. hypecalcaemia) are a common finding in patients with thymoma – reported in up to 67% of cases.
