Answer for BIR CoW 21 Dec 2025
Nodular fasciitis
Findings
1. Well‑defined lobulated intra-articular oval lesion (3.0 × 2.1 cm) situated in the anterior knee joint space, deep to the infrapatellar (Hoffa’s) fat pad. No frank bone erosion or marrow edema. 2. Lesion appears iso-intense in T1‑w images and heterogeneously hyperintense T2w images. No definite internal SWI blooming within the lesion. 3. On dynamic contrast sequences, lesion shows intense enhancement with progressive centripetal filling. Based on MRI morphologic and enhancement characteristics, the major differentials for a well-defined enhancing lesion in the anterior knee compartment include nodular fasciitis, tenosynovial giant cell tumour (localized type/PVNS), and intra-articular fibroma.
Discussion
HISTOLOGY: Well‑delineated proliferative spindle cell lesion with moderate cellularity showing histiocytic and spindled cells in storiform pattern with collagenous stroma. Focally, the tumor shows myxoid degeneration. This constellation of features is characteristic of nodular fasciitis, a benign, self-limited myofibroblastic proliferation. The presence of a storiform pattern, mixed myxoid and collagenous areas, and absence of atypia or hemosiderin deposition strongly aligns with this diagnosis. Nodular fasciitis is a self-limiting benign lesion characterized by a myofibroblastic proliferation in patients between 20 and 50 years. It usually appears as a palpable mass in the subcutaneous tissues and attached to the fascia. Intra-articular nodular fasciitis is rarely reported with only few cases have been documented in the literature. It is commonly misdiagnosed, and most cases are thought to be intraarticular diseases such us: pigmented villonodular synovitis, synovial chondromatosis, desmoid-type fibromatosis. Although intraarticular nodular fasciitis usually regress spontaneously and it does not recur in the follow up, almost all the patients reported in the literature underwent arthroscopic surgery to excise the lesion.
Findings
1. Well‑defined lobulated intra-articular oval lesion (3.0 × 2.1 cm) situated in the anterior knee joint space, deep to the infrapatellar (Hoffa’s) fat pad. No frank bone erosion or marrow edema. 2. Lesion appears iso-intense in T1‑w images and heterogeneously hyperintense T2w images. No definite internal SWI blooming within the lesion. 3. On dynamic contrast sequences, lesion shows intense enhancement with progressive centripetal filling. Based on MRI morphologic and enhancement characteristics, the major differentials for a well-defined enhancing lesion in the anterior knee compartment include nodular fasciitis, tenosynovial giant cell tumour (localized type/PVNS), and intra-articular fibroma.
Discussion
HISTOLOGY: Well‑delineated proliferative spindle cell lesion with moderate cellularity showing histiocytic and spindled cells in storiform pattern with collagenous stroma. Focally, the tumor shows myxoid degeneration. This constellation of features is characteristic of nodular fasciitis, a benign, self-limited myofibroblastic proliferation. The presence of a storiform pattern, mixed myxoid and collagenous areas, and absence of atypia or hemosiderin deposition strongly aligns with this diagnosis. Nodular fasciitis is a self-limiting benign lesion characterized by a myofibroblastic proliferation in patients between 20 and 50 years. It usually appears as a palpable mass in the subcutaneous tissues and attached to the fascia. Intra-articular nodular fasciitis is rarely reported with only few cases have been documented in the literature. It is commonly misdiagnosed, and most cases are thought to be intraarticular diseases such us: pigmented villonodular synovitis, synovial chondromatosis, desmoid-type fibromatosis. Although intraarticular nodular fasciitis usually regress spontaneously and it does not recur in the follow up, almost all the patients reported in the literature underwent arthroscopic surgery to excise the lesion.
Note:
We do not discourage differential diagnosis. But all the differentials must satisfy the findings noted in the case.
If you feel you have answered rightly but cannot find your name in the above list, please call 09551942599.
Did you Know?
The order in which the names appear in this winner's list is based on the time of submission. The first person to send the correct answer gets his/her name on top of the list!
We do not discourage differential diagnosis. But all the differentials must satisfy the findings noted in the case.
If you feel you have answered rightly but cannot find your name in the above list, please call 09551942599.
Did you Know?
The order in which the names appear in this winner's list is based on the time of submission. The first person to send the correct answer gets his/her name on top of the list!