Clinico-radiological-pathological correlation in eumycetoma spectrum: Case series

Abstract

Maduramycosis or mycetoma is one of the chronic granulomatous diseases commonly seen in tropical regions. Microbiological cultures and biopsy are carried out for the definitive diagnosis of the disease, but they are time-consuming methods. The present study aims to correlate clinical, radiological and pathological features in eumycetoma cases to emphasize the role of "dot in circle" sign leading to early imaging-based diagnosis. Imaging plays an important role in early diagnosis of mycetoma, which has therapeutic implications. "Dot in circle" sign is a recently described sign in mycetoma cases on ultrasound (USG) and magnetic resonance imaging (MRI). We diagnosed four cases of eumycetoma based on clinical and imaging features, which were confirmed with histopathology. The differential diagnosis, which may mimic this sign is also discussed. The "dot in circle" sign is seen on both ultrasound and MRI. This sign is highly specific for mycetomas. Knowledge of this sign can help in early diagnosis of mycetomas preventing misdiagnosis and further complications.

Keywords: Dot in circle; granulomatous; magnetic resonance imaging; mycetoma; ultrasound.

FIGURE 1

Components forming dot in circle on imaging.

FIGURE 2

Eumycetoma of the foot. (A) Soft tissue swelling at the dorsum of right middle toe and foot region with multiple encrusted skin sinuses. (B) Radiograph of the foot (AP view) appears normal except a soft-tissue density shadow over heads of 2–4^th metatarsals. (C) Ultrasound image shows multiple lesions (white arrows) with hypoechoic walls (circle) and hyperechoic foci in the center (dots) giving the appearance of “dot in circle”. (D, E) Axial T2-weighted (D) and STIR (E) MRI images showing multiple hyperintense lesions with hypointense periphery (black arrows) with central hypointense dots (white arrow) giving the appearance of “dot in circle”.

FIGURE 3

Eumycetoma of the great toe. (A) Swelling at the lateral aspect of the great toe with discharging sinus and foci of hyperpigmentation. (B) Radiograph of the foot (AP view) image shows soft-tissue density over the lateral aspect of the great toe (black arrow). (C) On ultrasound, multiple lesions (white arrows) are evident with thick hypoechoic walls and hyperechoic foci in the center. (D) Axial T2-weighted MRI shows multiple hyperintense lesions with central hypointense dots (white arrows).

FIGURE 4

Eumycetoma at the plantar aspect of the foot. (A) A protuberant swelling at the plantar aspect of foot with few encrusted sinuses. (B) Lateral radiograph of the foot appears normal except a soft-tissue density shadow on the plantar aspect (arrow). (C) On high-resolution ultrasound, multiple clustered lesions are noted, which have a hypoechoic periphery and hyperechoic center. (D–F) Axial STIR (D), T2WI (E), and Sagittal STIR (F) MRI images show multiple hyperintense lesions with central hypointense dots (white arrows) showing typical “dot in circle” sign in the subcutaneous plane.

FIGURE 5

Eumycetoma with bone involvement. (A) Soft-tissue swelling at the ankle on the medial side, extending into plantar aspect of foot with few encrusted sinuses and hyperpigemted patches in the skin. (B, C) AP and lateral radiographs of ankle show multiple osteolytic and sclerotic lesions in calcaneum with periosteal reaction (white arrows) at the lower end of tibia and fibula. (D) Ultrasound image shows multiple lesions with dot in circle sign (black arrows).

FIGURE 6

CT and MRI of the ankle of the patient with eumycetoma in Figure 5. (A, B) Sagittal and coronal reformats of CT of ankle show multiple osteolytic areas (black arrows) in calcaneum with periosteal reaction at the lower end of tibia and fibula (white arrows) with soft-tissue involvement, respectively. (C, D) Saggital and coronal STIR MRI images show multiple lesions in calcaneum and soft tissues with a dot in circle sign (arrows).

FIGURE 7

Eumycetoma on histology. (A) Haematoxylin and eosin (H&E) stain, low magnification, shows a cluster of fungal hyphae surrounded by the inflammatory response (B) GMS staining positive for fungal hyphae.

FIGURE 8

Dot in circle sign mimic – Phleboliths in a case of soft-tissue hemangioma in the foot (case not described in this series). (A) Sagittal STIR and (B) post-contrast T1W images show small phlebolith (arrow) in a hemangioma on the plantar aspect of the foot, which can give a similar appearance as a dot in circle sign.

FIGURE 9

Dot in circle sign mimics - Rice bodies (case not described in this series). Oblique sagittal STIR image of the elbow joint in a patient with articular tuberculosis. Multiple small hypointense nodular “rice bodies” are seen distending the joint and can mimic as a dot in circle sign.