Patho-morphological and immunohistochemical diagnosis of fibrous tissue pulmonary hamartoma in young buffaloes.

Hamartoma is a developmental disorder characterized by the presence of well-differentiated tissue, of multiple types, in excess at its normal location. The present study describes a fibrous tissue pulmonary hamartoma in two buffaloes. Grossly, there were large pale white masses present on the left diaphragmatic lobe in both cases. Microscopic examination of the lungs revealed that the bronchioles were dilated and showed many terminal respiratory bronchioles lined by a single layer of cuboidal epithelium supported by thick bands of collagenous tissue. Alveoli were distorted and separated by wide bands of connective tissues. Interalveolar septa were greatly expanded by collagen fiber proliferation and subsequent fibrosis. Fibrous connective tissues were demonstrated by immunohistochemistry (IHC) and Masson's Trichrome staining (MTS). Based on gross and histological examination, coupled with IHC and MTS, it was possible to confirm a case of hamartoma, which is rarely reported worldwide and is the first reported case from India.