Cat at home? Cat scratch disease with atypical presentations and aggressive radiological findings mimicking sarcoma, a potential diagnostic pitfall

Figures & data

Figure 1. Diagram depicting the patient population and the reasons for inclusion in our cohort.

Figure 3. Case no. 7. A 40-year-old female with an epifascial soft tissue lesion of the upper arm. (A) On a T1-weighted image, the lesion with intermediate signal intensity and irregular margin; wide contact with the underlying fascia (arrow). (B) Homogenous high T2-weighted signal intensity without any surrounding edema (arrow). (C) Coronal T1-weighted image with fat saturation after application of Gd-contrast shows heterogeneous contrast enhancement (arrow). (D–E) DWI image (D) with corresponding (E) ADC map shows diffusion restriction due to necrotic collection (circles).

Table 1. Summary of clinical, serological, pathological and molecular data

Case no.	Sex	Age	Swelling (days)	CRP (< 5 mg/L)	WBC count (< 11.3 G/L)	Biopsy	Histology	Serologic testing	PCR	Culture
1	m	26	38	0.6	4.8	IB	Granulomatous inflammation with necrosis	n.a.	pos	neg
2	m	16	29	21.9	11.2	n.d.	n.a.	1:256	n.a.	n.a.
3	f	22	28	0.6	6.6	n.d.	n.a.	1:64	n.a.	n.a.
4	m	36	42	2.1	5.1	EB	Granulomatous inflammation with necrosis	n.a.	pos	neg
5	f	12	23	1.0	7.6	n.d.	n.a.	1:256	n.a.	n.a.
6	f	26	17	1.1	6.3	CNB	Granulomatous inflammation with necrosis	n.a.	pos	neg
7	f	40	33	n.a.	n.a.	n.d.	n.a.	1:64	n.a.	n.a.
8	f	27	21	16.9	7.7	EB	Granulomatous inflammation with necrosis	1:256	pos	neg
9	m	74	150	3.6	6.2	CNB,	Granulomatous inflammation with necrosis,	n.a.	pos	neg
						IB, EB	metastasis of malignant melanoma
10	f	37	270	n.a.	n.a.	EB	Granulomatous inflammation with necrosis	n.a.	pos	n.a.

Legend: CNB: core-needle biopsy; CRP: C-reactive protein; EB: excision biopsy; IB: incision biopsy; n.a.: not available; n.d.: not done; neg: negative; PCR: polymerase chain reaction; pos: positive; WBC: white blood cell.

Table 2. MRI characteristics of the lesions with differential diagnosis

No.	A	B	C	D	E	F	G	H	I	J	K	L	M
1	n.a.	n.a.	n.a.	n.a.	n.a.	n.a.	n.a.	n.a.	n.a.	n.a.	n.a.	n.a.	n.a.
2	Distal UA (ST)	epi	28x45x28	c-s	inf	im	h	yes	rim	yes	no	Inflammation	Vascular lesion with internal bleeding
3	n.a.	n.a.	n.a.	n.a.	n.a.	n.a.	n.a.	n.a.	n.a.	n.a.	n.a.	n.a.	n.a.
4	Inguinal (ST)	epi	29x15x35	s	wd	h	h	no	hetero	yes	no	Pathologic LN	Soft tissue tumor (synovial sarcoma, neural tumor)
5	Distal UA (ST + B)	no	29x26x11	s	inf	im	h	yes	no	no	no	Inflammation; bone sarcoma	Osteomyelitis; bone tumor (Ewing sarcoma)
6	Distal UA (ST)	epi	26x14x24	s	inf	h	h	yes	hetero	yes	no	Inflammation; STS	venous structure; hematoma
7	Proximal UA (ST)	epi	18x6x21	s	inf	im	h	yes	rim	yes	no	Inflammation; nodular fasciitis; STS	Sarcoma
8	Proximal LA (ST)	epi	37x16x22	c-s	inf	im	h	yes	hetero	yes	yes	Pathologic LN; inflammation	Sarcoma/pathologic LN
9	Axilla (ST + LN)	epi	49x75x110	s	wd	h	h	no	hetero	yes	yes	Pathologic LN; STS	Liposarcoma
10.	Knee (ST)	epi	24x25x10	s	inf	im	h	yes	homo	no	no	Nodular fasciitis; inflammation, STS	Unclear lesion

A.Location (tissue type): B: bone; LA: lower arm; UA: upper arm, ST: soft tissue; LN: lymph node

B.Fascial relation: epi: epifascial

C.Size (mm)

D.Structure: c-s: Cystic-solid; s: Solid

E.Margin:inf: infiltrative; wd: well defined

F.T1-weighted sequence, h: high; im: intermediate

G.T2-weighted sequence, h: high

H.Surrounding edema

I.Enhancement hetero: heterogenous; homo: homogenous;

J.Necrosis

K.Satellite lesion(s)

L.Differential diagnosis (internal); LN: lymph node, STS: soft tissue sarcoma

M.Differential diagnosis (external): LN: lymph node, STS: soft tissue sarcoma;

n.a.: not available;

Table 3. Summary of treatment and follow-up

No.	Antibiotics	Treatment length (days)	Follow-up (days)
1	ciprofloxacin/doxycycline	55	60
2	clarithromycin	7	37
3	ciprofloxacin/doxycycline	11	11
4	none	−	59
5	clarithromycin	49	100
6	doxycycline	14	33
7	azithromycin	14	111
8	none	−	11
9	doxycycline + rifampicin	28	53
10	none	−	28